Self-contained die cushion with air saver



June 24, 1969 v. H. ANDERSON SELF-CONTAINED DIE CUSHION WITH AIR SAVER Filed Ju ly 13, 1967 INVENTOR. VINCENT H. ANDERSON W fwm afi ya ATTORNEii? United States Patent 3,451,667 SELF-CONTAINED DIE CUSHION WITH AIR SAVER Vincent H. Anderson, Canton, Ohio, assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed July 13, 1967, Ser. No. 653,165 Int. Cl. F16f 9/02; F15b 15/24 U.S. Cl. 267-1 12 Claims ABSTRACT OF THE DISCLOSURE Disclosure The present invention relates to the art of self-contained die cushions, and more particularly to a self-contained die cushion having an air saver or reservoir incorporated therewith.

This invention is particularly applicable for use in a power press wherein depending rods are used to support a hold-down ring of a drawing die, and it will be described with particular reference thereto; however, it is appreciated that the invention has much broader applications and may be used in various other environments wherein a die cushion is required.

Many dies used within power presses incorporate holddown rings or other auxiliary elements which are controlled, to a certain extent, by a die cushion located below the bed of the power press. These die cushions take a variety of forms; however, the most common die cushion includes two telescoped sleeves with end walls defining an internal cushion chamber filled with a compressible fluid which biases the upper sleeve in an upwardly direction. A plurality of rods extending downwardly from the die within the press rests upon the upper sleeve. These rods coact with movable elements within the die so that the sleeve is forced downwardly by the rods during the downward stroke of the press. The downward movement of the upper sleeve compresses the fluid within the cushion chamber so that the rods are forced in an upward direction by the upper sleeve during the upward stroke of the power press. The volume of air, or other compressible fluid, within the chamber of the die cushion is quite large to provide the necessary biasing action for the downwardly extending rods. This presents a substantial difiiculty.

When a die is to be repaired or replaced, the die cushion must be dropped into an inoperative position. One common way of accomplishing this is to exhaust most of the fluid from the chamber of the die cushion. This requires a substantial amount of time to exhaust and then replace the large volume of fluid within the die cushion. In an eflort to reduce the time for exhausting and filling the chamber of the die cushion, relatively large supply hoses have been used. These are expensive, and they do not substantially reduce the total time required to drop the die cushion into its inoperative position and then raise the die cushion into its operative position. To overcome the disadvantages of this particular arrangement, it has been suggested that a fluid reservoir should be mounted adjacent the die cushion with a valve between the reservoir and the cushion. When the die cushion is to be dropped, the valve is opened to store fluid within the reservoir. The valve was then closed so that the fluid would remain in the reservoir. To raise the die cushion, the valve was again opened which allowed flow of fluid back to the die cushion. This again involved complex and expensive mechanical arrangements to accomplish the operation of the die cushion.

The structure explained above has been modified to provide the reservoir and valve within the die cushion itself. When this is done, the piping between the reservoir and the die cushion chamber is eliminated; however, certain inherent disadvantages are built in. The valve be tween the reservoir and die cushions must be operated, mechanically, from a position outside of the die cushion. Thus, a rod or other valve operating means must be provided internally of the die cushion.

The disadvantages of the prior die cushions are completely overcome by the present invention which is a completely new concept to the art of die cushions and includes a simplified structure which will allow movement of the die cushion between its upward operative position and its lower inoperative position.

In accordance with the present invention, there is provided an improvement in a self-contained die cushion which includes a movable, operative member having an inoperative lower position and an operative upper position, a fluid means for biasing the member in the upper direction at least when the member is in the operative position, this fluid means includes a cushion chamber filled with a compressible fluid, means for dividing the chamber into first and second chamber portions, and a fluid passage for communicating the chamber portions. The improvement in accordance with the invention includes the provision of an element in the chamber and movable in a first direction when pressure in the first portion approximately equals or exceeds the pressure in the second portion and in a second direction when pressure in the first portion is substantially less than pressure in the second portion. A valve means, carried by the element, opens the fluid passage when the element moves a selected amount in the first direction and closes the fluid passage when the element moves a selected amount in the second direction. There are also provided means for limiting the movement of the element in at least the second direction and means for exhausting fluid from the first portion of the chamber where-by, upon such exhaust, the pressure in the first portion is decreased, the communicating passage is closed, and the members allowed to drop into its inoperative position.

-By constructing a die cushion in accordance with the invention as defined above, the upper, or first, portion of the cushion chamber is exhausted. This closes the lower portion and maintains or saves air therein. Consequently, only a small amount of air is exhausted to drop the die cushion into its inoperative position. To raise the cushion back into the operative position, it is only necessary to pump a relatively small amount of air into the upper portion of the cushion chamber. This air increases the pressure within this portion and automatically opens the valves between the upper and lower portions of the die cushion chamber. When this valve opens, both portions of the cushion chamber are interconnected so that the air in the complete chamber, i.e., both the upper and lower portions, provides the working bias of the die cushion. It is readily apparent that this arrangement provides an efiicien-t and realtively simple structure for saving a certain portion of air within the die cushion between successive shifts in the condition of the cushion.

The primary object of the present invention is the provision of a self-contained die cushion which is inexpensive to produce, usable in existing presses without modification and easily and rapidly dropped into the inoperative position and raised into the operative position with a minimum of fluid.

Another object of the present invention is the prov-ision of a self-contained die cushion which requires a lesser amount of air, or fluid, to shift from the inoperative position to the operative position.

Yet another object of the present invention is the provision of a self-contained die cushion which incorporates two separate fluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and one of which is exhausted to drop the cushion into its inoperative position.

Still a further object of the present invention is the provision of a self-contained die cushion which incorporates two separate fluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and the first of which is exhausted to drop the cushion into its inoperative position While a valve seals the second from being exhausted.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiment of the invention as read in connection with the accompanying drawing in which the single figure is a partial, cross-sectional side view illustrating, somewhat schematically, the preferred embodiment of the present invention.

Referring now to the drawing wherein the showing is for the purpose of illustrating the preferred embodiment of the invention only, and not for the purpose of limiting same, there is illustrated a die cushion A constructed in accordance with the present invention. This die cushion includes a stationary lower cylinder and a sleeve 12 telescopically received over the cylinder 10. The lower portion of the cylinder is provided with an end plate or closure plate 14 secured, by appropriate means (not shown), onto a support plate 16. A recessed portion 18 is provided adjacent the lower end of cylinder 10, and an upper flange or abutment 20 is provided adjacent the upper end of the cylinder. As clearly illustrated, the reciprocating sleeve 12 includes an upper end wall 22 having an upper bearing surface 24. This bearing surface contacts the control rods 26 which function to bias or move certain elements in a power press die mounted above the cushion A. The lower end of sleeve 12 includes a stop flange 28 which coacts with the recessed portion 18 to limit the upwardmost position of the sleeve 12 with respect to the cylinder 10.

The space within the cylinder 10 and the sleeve 12 defines a compressible fluid filled cushion chamber which is divided into an upper portion 30 and a lower portion 32. These portions are hereinafter referred to as chambers or chamber portions. As will be explained later, these chamber portions combine during normal operation to provide the necessary upward bias against sleeve 12 to force the rods 26 in an upward direction or to control the downward movement of rods 26.

Within the die cushion there is provided an upstanding tube 40 threadably secured to end plate 14. This tube includes an interior sleeve 42 spaced from the inner wall of the tube 40 by an appropriate spacer 43. In this manner, an annular passage 44 and a separate interior passageway 46 are provided within the tube 40. This lastmentioned passageway includes a lower inlet 50 and an upper outlet 52 communicated directly with the upper chamber 30. Adjacent the upper end of tube 40 there is provided a collar 54 which secures a washer 56 against a snap ring 58. The tube is also provided with a plurality of upper orifices 60 normally communicated with the chamber 30 and lower orifices 62 normally communicated with chamber 32. For a purpose to be described later, there is provided a lower stop abutment 64 extending radially outwardly from the tube 40.

Within the stationary cylinder 10, there is provided a floa g pis on 70 having a peri heral seal 72 which prevents fluid flow around the periphery of the piston between the upper chamber portion 30 and the lower chamber portion 32. integrally formed with the piston is a valve element having an internal valving surface 74 which is also a journal bore. Spaced axially in this bore are an upper seal 76 and a lower seal 78. The piston is biased downwardly by a spring 80 acting against the washer 56. The downwardmost position of piston 70 is limited by stop abutments 64 while the uppermost position is limited by the flange 20. Consequently, the floating piston 70 is freely movable between the two aforementioned abutments.

Adjacent the lower portion of the die cushion there is provided an appropriate fluid system including an inlet line 92 for a compressible fluid, such as air, under a pressure generally in the range of 60l00 p.s.i. This inlet line feeds two branches 94, 96. The first branch is communicated with the chamber 32 through a restricted orifice 97. The second branch includes a restriction 98 and is used to direct fluid, in a selected manner, into the upper chamber portion 30. This fluid flows through passageway 46 by way of an inlet line 100. An exhaust line 102 is communicated with line through a rotary valve 104 having an internal valve passage 106. The position of the valve 104 determines whether line 100 is communicated with pressurized fluid, such as air, in branch 96 or with the exhaust line 102.

Referring now to the operation of the die cushion A, during normal operation of the die cushion, the sleeve 12 reciprocates between positions a and b. As the press moves downwardly, the rods 26 force sleeve 12 from position a to position b. This compresses the air within the chamber portions 30 and 32 which are directly communicated, in a manner to be described later. Thereafter, the compressed air forces the rods 26 in an upward direction as the press starts the upper portion of its cycle. This is the general operation of the die cushion A; however, when the die is to be replaced or repaired, it is necessary to drop the die cushion into a lower position represented by c. The die cushion is illustrated in this downward, inoperative position.

When the die cushion is in its inoperative position, as shown in the figure, the chamber 30 is exhausted through line 102. The weight of sleeve 12 allows the sleeve to drop. Compressed air within the chamber 32 cannot escape into chamber 30 because the piston 70 is moved into its upper position due to the high pressure difierential between the chambers 30 and 32. In this position of the piston, orifices 60 are closed by valving surface 74 to isolate the chamber 32 from the upper exhausted chamber 30.

In order to again move the sleeve 12 into the upper operative position, valve 104 is turned so that line 100 is connected through restriction 98 with inlet 92. In this manner pressurized air is forced through outlet 52 and the pressure within chamber 30 is increased. This raises the sleeve '12. As the pressure increases within chamber 30, the floating piston 70 moves downwardly, at first a slight amount. This slightly opens the orifices 60 which allows pressurized fluid within chamber 32 to flow into the chamber 30. When this happens, the piston 70 moves more rapidly in a downward direction to open the orifices 60 so that chambers 30 and 32 are in direct communication. Sleeve 12 is moved rapidly into the position a. Thereafter, reciprocal movement of the sleeve 12 takes place against the total volume of air, or fluid, within the chambers 30,- 32. It is appreciated that a relatively small volume of air is required to shift the die cushion into its operative position. The chamber 32 serves as an air saver or reservoir within the cushion itself.

When the die cushion is to be shifted into its inoperative position, the valve 104 is again moved to the position illustrated in the figure. At this time, air rushes through the passageway 46 to exhaust the chamber 30. This immediatel creates a lesser pressure Within chamber 30 than the pressure within chamber 32. Consequently, the floating piston 70 moves upwardly to close the orifices 60 whereby the volume of air within the chamber 32 is entrapped and sealed from being exhausted through the line 102. It is appreciated that a relatively small volume Olf air must be removed before the chamber 30 is exhausted and the weight of the sleeve '12 drops the sleeve into its inoperative position c. Spring 80 biases the piston 70 in a downward direction to assist in the initial opening of the orifices 60.

From the above description, it is appreciated that selfcontained die cushion A is fail safe in operation. When the die cushion is dropped into its inoperative position, the high pressure within chamber 32 assures that passage of compressible fluid through orifices 60 cannot take place. Any leakage around thevarious seals will be gradual and will be expelled through exhaust line 102 without forcing the sleeve 12 in an upward direction. Thus, there can be no inadvertent shifting of the die cushion into its operative position upon failure of any element within the die cushion A. If leakage takes place in chamber 32, the air is replaced within this chamber through the inlet branch 94. For this reason, the pressure within the chamber 32 is maintained at line pressure, which is the normal optimum pressure for the die cushion. In addition, the restricted orifice 97 is a small passage, and it prevents fluid shock within the inlet line 92 during normal operation of the die cushion.

By using the spring 80, the piston 70 is moved downwardly when the pressures in chambers 30, 32 are approximately the same. This assures that the orifices 60 are opened as the chamber 30 is filled and during normal operation of the cushion. Also, this spring prevents alternate opening and closing of the orifices 60 during normal operation of the cushion.

The present invention has been described in connection with one structural embodiment; however, it is appreciated that various changes may be made in this embodiment.

Having thus described my invention, I claim:

1. In a self-contained die cushion including a movable, operative member having an inoperative lowered position and an operative upper position, a fluid means for biasing said member in an upward direction at least when said member is in the operative position, said fluid means including a cushon chamber filled with a compressible fluid, means for dividing said chamber into first and second portions, and a fluid passage for communicating said portions, the improvement comprising: an element in said chamber movable in a first direction when pressure in said first portion approximately equals or exceeds the pressure in said second portion and in a second direction when pressure in said first portion is in said first direction and for closing said fluid passage when said element moves a selected amount in said second direction, means for limiting the movement of said element in at least said second direction, and means for exhausting fluid from said first portion whereby said pressure in said first portion is decreased, said passage is closed, and said member is allowed to drop into the inoperative position.

2. The improvement as defined in claim 1 including a spring means for biasing said element in sad first direction.

3. The improvement as defined in claim 1 including a stationary tube extending in said chamber, said passage being formed in said tube, a first orifice means for communicating said passage with said first portion, a second orifice means for communicating said passage with said second portion, and said valve means comprising a sleeve surrounding said tube and connected to said element with said sleeve closing at least one of said orifice means when said element moves in said second direction.

4. The improvement as defined in claim 3 wherein said element forms at least a portion of said dividing means.

5. The improvement as defined in claim 3 wherein said exhausting means includes a passageway extending through said stationary tube.

6. The improvement as defined in claim 1 including a fluid inlet means for filling said chamber, said inlet means including a fluid inlet line communicated with said first portion of said chamber.

7. The improvement as defined in claim 6 including means in said line for restricting flow into said chamber.

8. The improvement as defined in claim 1 including means for limiting the movement of said element in said first direction.

9. The improvement as defined in claim 1 wherein said cushion chamber is defined in part by a stationary cylinder and said dividing means is a piston reciprocally mounted in said cylinder.

10. The improvement as defined in claim 9 wherein said element is secured to and is movable with said piston.

11. The improvement as defined in claim 9 including a stationary tube extending in said cylinder and said piston includes an aperture through which said tube extends.

12. The improvement as define din claim 11 wherein said tube includes said passage and a passageway means communicated to said first portion for filling said chamber with compressible fluid.

References Cited UNITED STATES PATENTS 2,924,446 2/1960 Williamson 2671 EVON C. BLUNK, Primary Examiner.

DANIEL F. WORTH III, Assistant Examiner. 

